/**
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#ifndef MEM_H_MODULE
#define MEM_H_MODULE

/*-****************************************
*  Dependencies
******************************************/
#include <stddef.h>     /* size_t, ptrdiff_t */
#include <string.h>     /* memcpy */


/*-****************************************
*  Compiler specifics
******************************************/
#define MEM_STATIC static __inline __attribute__((unused))

/* code only tested on 32 and 64 bits systems */
#define MEM_STATIC_ASSERT(c)   { enum { MEM_static_assert = 1/(int)(!!(c)) }; }
MEM_STATIC void MEM_check(void) { MEM_STATIC_ASSERT((sizeof(size_t)==4) || (sizeof(size_t)==8)); }


/*-**************************************************************
*  Basic Types
*****************************************************************/
#include <stdint.h>
typedef   uint8_t BYTE;
typedef  uint16_t U16;
typedef   int16_t S16;
typedef  uint32_t U32;
typedef   int32_t S32;
typedef  uint64_t U64;
typedef   int64_t S64;
typedef  intptr_t iPtrDiff;
typedef uintptr_t uPtrDiff;


/*-**************************************************************
*  Memory I/O
*****************************************************************/
MEM_STATIC unsigned MEM_32bits(void) { return sizeof(size_t)==4; }
MEM_STATIC unsigned MEM_64bits(void) { return sizeof(size_t)==8; }

MEM_STATIC unsigned MEM_isLittleEndian(void)
{
	const union { U32 u; BYTE c[4]; } one = { 1 };   /* don't use static : performance detrimental  */
	return one.c[0];
}

MEM_STATIC U16 MEM_read16(const void* memPtr)
{
	U16 val; memcpy(&val, memPtr, sizeof(val)); return val;
}

MEM_STATIC U32 MEM_read32(const void* memPtr)
{
	U32 val; memcpy(&val, memPtr, sizeof(val)); return val;
}

MEM_STATIC U64 MEM_read64(const void* memPtr)
{
	U64 val; memcpy(&val, memPtr, sizeof(val)); return val;
}

MEM_STATIC size_t MEM_readST(const void* memPtr)
{
	size_t val; memcpy(&val, memPtr, sizeof(val)); return val;
}

MEM_STATIC void MEM_write16(void* memPtr, U16 value)
{
	memcpy(memPtr, &value, sizeof(value));
}

MEM_STATIC void MEM_write32(void* memPtr, U32 value)
{
	memcpy(memPtr, &value, sizeof(value));
}

MEM_STATIC void MEM_write64(void* memPtr, U64 value)
{
	memcpy(memPtr, &value, sizeof(value));
}

MEM_STATIC U32 MEM_swap32(U32 in)
{
#if defined (__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 403)
	return __builtin_bswap32(in);
#else
	return  ((in << 24) & 0xff000000 ) |
			((in <<  8) & 0x00ff0000 ) |
			((in >>  8) & 0x0000ff00 ) |
			((in >> 24) & 0x000000ff );
#endif
}

MEM_STATIC U64 MEM_swap64(U64 in)
{
#if defined (__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 403)
	return __builtin_bswap64(in);
#else
	return  ((in << 56) & 0xff00000000000000ULL) |
			((in << 40) & 0x00ff000000000000ULL) |
			((in << 24) & 0x0000ff0000000000ULL) |
			((in << 8)  & 0x000000ff00000000ULL) |
			((in >> 8)  & 0x00000000ff000000ULL) |
			((in >> 24) & 0x0000000000ff0000ULL) |
			((in >> 40) & 0x000000000000ff00ULL) |
			((in >> 56) & 0x00000000000000ffULL);
#endif
}

MEM_STATIC size_t MEM_swapST(size_t in)
{
	if (MEM_32bits())
		return (size_t)MEM_swap32((U32)in);
	else
		return (size_t)MEM_swap64((U64)in);
}

/*=== Little endian r/w ===*/

MEM_STATIC U16 MEM_readLE16(const void* memPtr)
{
	if (MEM_isLittleEndian())
		return MEM_read16(memPtr);
	else {
		const BYTE* p = (const BYTE*)memPtr;
		return (U16)(p[0] + (p[1]<<8));
	}
}

MEM_STATIC void MEM_writeLE16(void* memPtr, U16 val)
{
	if (MEM_isLittleEndian()) {
		MEM_write16(memPtr, val);
	} else {
		BYTE* p = (BYTE*)memPtr;
		p[0] = (BYTE)val;
		p[1] = (BYTE)(val>>8);
	}
}

MEM_STATIC U32 MEM_readLE24(const void* memPtr)
{
	return MEM_readLE16(memPtr) + (((const BYTE*)memPtr)[2] << 16);
}

MEM_STATIC void MEM_writeLE24(void* memPtr, U32 val)
{
	MEM_writeLE16(memPtr, (U16)val);
	((BYTE*)memPtr)[2] = (BYTE)(val>>16);
}

MEM_STATIC U32 MEM_readLE32(const void* memPtr)
{
	if (MEM_isLittleEndian())
		return MEM_read32(memPtr);
	else
		return MEM_swap32(MEM_read32(memPtr));
}

MEM_STATIC void MEM_writeLE32(void* memPtr, U32 val32)
{
	if (MEM_isLittleEndian())
		MEM_write32(memPtr, val32);
	else
		MEM_write32(memPtr, MEM_swap32(val32));
}

MEM_STATIC U64 MEM_readLE64(const void* memPtr)
{
	if (MEM_isLittleEndian())
		return MEM_read64(memPtr);
	else
		return MEM_swap64(MEM_read64(memPtr));
}

MEM_STATIC void MEM_writeLE64(void* memPtr, U64 val64)
{
	if (MEM_isLittleEndian())
		MEM_write64(memPtr, val64);
	else
		MEM_write64(memPtr, MEM_swap64(val64));
}

MEM_STATIC size_t MEM_readLEST(const void* memPtr)
{
	if (MEM_32bits())
		return (size_t)MEM_readLE32(memPtr);
	else
		return (size_t)MEM_readLE64(memPtr);
}

MEM_STATIC void MEM_writeLEST(void* memPtr, size_t val)
{
	if (MEM_32bits())
		MEM_writeLE32(memPtr, (U32)val);
	else
		MEM_writeLE64(memPtr, (U64)val);
}

/*=== Big endian r/w ===*/

MEM_STATIC U32 MEM_readBE32(const void* memPtr)
{
	if (MEM_isLittleEndian())
		return MEM_swap32(MEM_read32(memPtr));
	else
		return MEM_read32(memPtr);
}

MEM_STATIC void MEM_writeBE32(void* memPtr, U32 val32)
{
	if (MEM_isLittleEndian())
		MEM_write32(memPtr, MEM_swap32(val32));
	else
		MEM_write32(memPtr, val32);
}

MEM_STATIC U64 MEM_readBE64(const void* memPtr)
{
	if (MEM_isLittleEndian())
		return MEM_swap64(MEM_read64(memPtr));
	else
		return MEM_read64(memPtr);
}

MEM_STATIC void MEM_writeBE64(void* memPtr, U64 val64)
{
	if (MEM_isLittleEndian())
		MEM_write64(memPtr, MEM_swap64(val64));
	else
		MEM_write64(memPtr, val64);
}

MEM_STATIC size_t MEM_readBEST(const void* memPtr)
{
	if (MEM_32bits())
		return (size_t)MEM_readBE32(memPtr);
	else
		return (size_t)MEM_readBE64(memPtr);
}

MEM_STATIC void MEM_writeBEST(void* memPtr, size_t val)
{
	if (MEM_32bits())
		MEM_writeBE32(memPtr, (U32)val);
	else
		MEM_writeBE64(memPtr, (U64)val);
}


/* function safe only for comparisons */
MEM_STATIC U32 MEM_readMINMATCH(const void* memPtr, U32 length)
{
	switch (length)
	{
	default :
	case 4 : return MEM_read32(memPtr);
	case 3 : if (MEM_isLittleEndian())
				return MEM_read32(memPtr)<<8;
			 else
				return MEM_read32(memPtr)>>8;
	}
}

#endif /* MEM_H_MODULE */